Gas-purification process and apparatus



GAS PURIFICATION PROCESS AND APPARATUS Original Filed June 6, 1924 2 Shees-Shee'f.l l

Nov. 6, 1928. 1,690,437

F. W. SPERR, JR

GAS PURIFICATION PROCESS AND APPARATUS Original Filed June 6, 1924 2 Sheets-Sheet 2 Pwd Nev. 6,1928.

UNi'ri-:D STATE-s IPa'riiN'r oFFicE.

Imm W. m In., l' PITTSBURGH, IPENIBYITAIIIA,y ABSIGNOB T0 THE m OOIPANY. 0l PITTSBURGH, PENNSYLVANIA, A OOBRORATION 0l' PENN- IYLVAIIA.

GAi-PUmICATION PROCESS AND APnPARATUS.

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, This invention relates to pr aratus for thetpuriication of 1 Eind involving e ste with an impurity absor inm ap 16 Ser. o. 18,258, filed June 6, 1924.

'Die invention consists broadly in removing the last traces of impurities (for example hydrogen sulphide) from the gas, after the greater rtion thereof has already been removed tlprefnm by a iirst waishingl,1 by subecting esai gastoasecon was ingeniilying freshly regenerated airwashing liqui Asthe air washing licuid is but slightly a5 deteriorated by absorbing the traces o impurities rem in the gas after its first washing the liquid coming from the second w can' conveniently be conveyed godly to theair scrubber and employed ao therein for washing the air.

The rocess of the resent invention is articular y eective w en carried out wi a y freshly precipitated iron compound as the air puri g agent as described in the above as mentioned specification, and a further gain i n eciency can be achieved by employing un i directional iiow of air and washing liquid in the air scrubber in accordance with the invention described inthe application of Gilbert en Edward Seil,A Ser. No. 18,204, filed June 6,

V 1924, filed of even date herewith.

The apparatus for canying out the new process, comprising means o transferring impurities 4l from the gas to a stream of air in combination with a scrubber for purifying the air, a secondary absorber for removing the last traces of impurities from the gas, and a system for circulating the air washing liquid through thel -secondary gas absorber and the air scrubber in succession.

The invention further consists in such other new and useful improvements, and-has for further objects such other operative advanstood, there will now be descr invention also-consists in providing capable of reacting with the tages or results, as may be found to obtain 1n the and apparatus hereinafter descn or claimed.

In order that the invention iia be under- -example and with reference to the accompanying drawings, a preferred ,mode of carrying ,out the process and two arrangements of a paratus with which the process may be carried out, as ap hed to the elimination of ,hydrogen sulphi' e from coal gas.

In these drawings: Fi re 1 is a neral elevational view of a by way of comp ete plant or the elimination of hydrogen sulphide from coal gas.A

Figure 2 is a similar view of a modied plant in which all the absorbers and actiliersare combined into a single structure.

In both figures of these drawings similar reference numerals refer to corresponding parts. v

In the specific instance now to be described,

coal gas is purified from hydrogen sulphide and other acid impurities, employing the sp cial steps described in the other ications of even date above mention The rst washin by which about 90% of the H,S isl i remove ,'is effected with a solution of sodium carbonate in a scrubber 1 into which the gas enters at the inlet 2, flows upwardl in countercurrent with the washin solution delivered through a pipe 3,.an is discharged through the pipe 4. In the scrubber 1 the hydrogen sulphide is transferred to,the sodium carbonate solution which flows from the bottom of the scrubber through pipes 5 and a set of sprayers 6 into the top of the actiier 7. The solution falls through the actier 7 to the bottom thereof and flows oi ithrough a pipe 8 into a sump 9 from which l'it is withdrawn by a pump 10 and pipe 11, and thence recirculated to the top o f the absorber. The solution traverses' the actifier 7 downwardly in countercurrent with a stream of air supplied by a blower 12, whereby the alkaline solution is regenerated and the hydrogen sulphide transferred to the air. The air leaves the actiiier by a pipe 13 'and is conveyed to the top of another scrubber or tower 14. In the scrubber 14 the air is washed with a liquid containing an iron compound which is llilydro n sulphide with formation of iron s phi e preferably a dilute solution of sodium carbo nate ' four chambers 1, 72 14,

containin ferrie carbonate or other iron compond, fres 1y precipitated as described in my aforesaid application filed of even date herewith. The wash liquid is introducedV also at the top of the towel' through pipes 15 and s rayers 16 and after traversing the scrubber ownwardl that is in the same direction as the air, itjioivs off through a pipe 18 into a sump 19. lcan air is discharged through the pipe 17. The liquid is regenerated concurrently with the purification of the air while traversing the scrubber 14 and the regeneration is completed in the sump 19 by means of air jets 20 which also agitata the liquid and mechanically float the sulphur to the surface thereof from which it is readily removed by skimmin and then dried in the centrifuge 28. Accor 'ii to the present invention the artly puri ed gas discharged from the scrubber l is conveyed to the bottom of a second scrubber 30 b means of the pipe 4. In this scrubber 30 tiie gas is subjected to a second washing by counterllow with fully regenerated air washing liquid from the sump 19 where by the.last traces of hydrogen sulphide are extracted, and the com letely purified gas leaves the installation t ough the pipe 31. The air washing liquid, consisting as already described of a solution of sodium carbonate containing an iron compound in suspension, is pumped from the sum 19 by the pump 24 and through pi es 23, 32, and sprayers, to the top of the absor er 30. After fallingthrou hthe absorber and absorbing the last traces o H,S from the gas the liquid enters the pipes 1 5 and passes into the air scrubber 14 as already described. The air washing liquid thus traverses the second gas scru ber and the air scrubber in series, and bein completely regenerated as well as containing freshly preci pitated iron compound introduced by means of the feed tank 21, when it enters the second gas scrubber, it has great avidity for hydrogen sulphide and is extremely effective in absorbing the last traces of the same from the gas. The amount of hydrogen sulphide thus absorbed being comparatively small, it does not interfere with the sub uent operation of the liquid in the air scrub er 14.

In the installation shown mary absorber 1 and the actifier 7 are combincd into a sin le tower so organized that the liquid flows y gravity from the upper to the lower compartment in accordance with the invention described in the specification of U. S. Letters Patent No. 1,478,543, Bird, granted to The Koppers Company; also the secondary absorber 30 and the air scrubber 14 are similarly combined into a single tower.

In the modification shown in Fig. 2, all 30 are combined into a single tower, which is divided by a longitudinal partition 33, the left hand section containing the primary absorber 1 and the actilier 7 while the right hand section contains in Fig. 1 the pri- 11 ber 14. The

gas pipe 4 and the air pipe 13 connectin the two towers ofthe installation shown in ig. 1 are eliminated. a'lhe gas enters 'the primary absorberl` through 'the inlet 2 at the bottom tliereof, flows' upwardly through the said absorber, passes into the top of the secondary absorber 30 through an opcning 4 in the partition 33, flows downwardly through this outlet 31 at sorber30. Y i r:

The air enters the actilier7 at `the bottom, flows upward] and asses through an opening 13a rovi ed ywit an air baille, into the top of t e air scrubber 14, throu h which it flows downwardly and escapes at t e outlet 17.

The sodium carbonate solution fromthe sump 9 is pumped to the to of the-left'hand section of the tower and gescends throu h the bottom of thezsecondaryfabboth compartments land 7 in series, whilethe solution containing the preci itatediron compound from the sump 19 similarly descends through the compartments 30 14 of the right hand section in series. arrangement provides a very convenient'and compact installation.r l

The invention as hereinabove set forth or exemplified may embodied within the scope of the claims hereinafter made. l

I claim:

1. A process of the kind referred to for purifying gases, characterized by the gas, after the greater portion of e imurities have been removed therefrom b a st washing, to a second washing emp oying freshly regenerated air washing liquid, for the purpose described.

2. A process as claimed in claim 1 in which the air washing liquid is used for the second gas washing and for the air washing in direct succession and in the orderl stated.

3. A process as claimed in claim 1 applied to the elimination of hydrogen sulphide from coal gas and like fuel gases.

4. A rocess as claimed in claim 1 applied to the e ination of hydrogen sulphide from coal gas and like fuel ases and in which the 'quid employed for t e second wash' and the air washing is a dilute tion containing a compound.

5. A process as claimed in claim 1, in which the air and the washing liquid for same both traverse the air scrubber in the same direction.

6. A process as claimed in claim 1 a Pplied to the elimination of hydrogen sul hide from coal gas and like fuel gases an in which about 90% of the hydrogen sulphide is absorbed in the first washin with alkaline li uid and the remainder o the hydrogen sufiphide absorbed in the second washing with the li uid whereof the primary function is to was the air.

aline solufreshly precipitated iron absorber andis discharged at the be variously practiced or sub'ecting mg iis 7. Apparatus for carrying out the process claimed in claim 1, com r1s' means for transferrin impurities flr'om t e gas to a stream of a1r, in combination with a scrubber for purifying the air, a secondary absorber for removing the last traces of impurities from the gas, and a system for simulating the air washing liquid throughthe secondary gas absorber and the air scrubber in succession.

8. Apparatus as claimed in 'claim 7, in which the means for transferring impurities from the gas to a stream of air include an absorber and an actifier arranged in superposition in a single tower, and in which the seoy phide is absorbed in the first washing' with a.v `solution of sodium carbonate and the remainder of the hydrogen sulphide absorbed in the second washing with the liquid whereof 25 the primary function is to wash the air.

In testimony whereof I have hereunto set my hand.

FREDERICK W. SPERR, JR. 

